The invention relates to a printer, and more particularly relates to a mechanism of a printer for transporting a printing paper to be printed in a direction toward a printing head and a platen and in a direction away from the printing head and the platen wherein the mechanism may be easily assembled with a required precision without any special adjustments of the related elements.
With a recent wide spread of personal computers and word processors, so called the office appliances generally used in many offices, printers have come to be used in combination with such appliances. The printers are provided with a printing head including characters, wires, etc., to effect printing on a printing paper in cooperation with a platen arranged opposite to the printing head with a clearance therebetween for passing the printing paper therethrough. In these printers the printing paper is transported in the direction transversely of the platen by means of a pair of frictional rollers provided on one side of the platen transversely thereof and another pair of frictional rollers provided on the other side of the platen transversely thereof while the printing paper is guided by a paper guide mechanism provided between the two pairs of frictional rollers. Generally the paper transporting mechanism includes rotational rollers rotatably mounted between the frames of printer for transporting the printing paper and guide plates arranged between the rotational rollers for guiding the printing paper. It has therefore been required to assemble these separate and individual transporting rollers and guide plates while they are precisely adjusted to each other to correctly determine the paper transporting path with respect to the printing head and the platen in a manner as to keep the printing paper clean from the ink platen or ink ribbon, and free from being materially damaged, and also to avoid causing noises during the printing operation. Especially in a polychrome printer having a platen having a number of porous elements arranged therearound each impregnated with an ink of different color, it is required to reduce to the smallest possible the clearance between the platen and the printing paper in order to avoid causing undesired noises during the printing operation. In this case, the failure of required adjustments will often spoil the printing paper with the ink of platen as the latter is transported.